The present invention relates to apparatus for clamping substrates in vacuum processing chambers, and in particular, to apparatus and methods for releasably clamping the substrate to a support structure within a vacuum processing chamber, for example, in a plasma processing system.
Plasma processing of substrates, such as semiconductor wafers and films, is typically performed in vacuum processing chambers (vacuum chambers). Within these vacuum chambers during plasma processing, the generated plasma could potentially raise the temperature of the substrate, for example, a wafer, to a level where it becomes damaged, so as to not be usable.
To prevent thermal damage in these substrates from high temperatures, various cooling techniques and systems therefore have been developed. One such system involves conductively cooling the substrate on its xe2x80x9cbacksidexe2x80x9d, the side opposite the side (front side) being plasma processed, typically by conductive cooling with Helium. This cooling technique is commonly known as xe2x80x9cback side coolingxe2x80x9d.
Typical vacuum chambers that facilitate back side cooling have substrate support structures, commonly referred to as chucks. These chucks typically include a pattern of grooves, for maintaining helium gas passage. The flowing helium gas, or other backside gas, cools the substrate by thermal contact between the substrate and the chuck. The helium or other backside gas is typically introduced at pressures higher than the ambient pressures of the vacuum processing chambers. Accordingly, the substrates must be clamped to the chucks, to maintain the helium on the back side of the substrate and to prevent the substrate from moving, as movement will typically cause the substrate to move out of its original alignment with respect to the processing system. Once out of alignment, the substrate may be missed by an arm or other transport mechanism that picks up the substrate after plasma processing, whereby the substrate is not moved to the next processing stage and the process must be stopped for manual intervention. This results in costly down time until the process can be resumed. Alternately, the substrate may be damaged by collisions between arm members and the substrate edges, as the arm members may strike the misaligned substrate upon attempting to grasp it.
Substrates are clamped to chucks, for example, by mechanical or electrostatic clamping mechanisms. Many clamping mechanisms employ O-rings or lip-type seals, for maintaining the substrate on the chuck and sealing the substrate thereto, to prevent helium or other backside gases from leaking into the ambient (vacuum) environment of the vacuum processing chamber.
These O-ring seals exhibit several drawbacks. For example, O-rings require high compression rates for adequately sealing substrates to chucks. As a result, the substrates can be damaged upon contact with the O-rings, even before chucks are brought into contact with them, as these high pressures cause distortion in the substrates. Distortion damage stresses the substrate and can result in breakage of the substrate.
Additionally, after processing, the O-rings may adhere to the substrate. This adherence prevents the arm or transport mechanism from picking up the processed substrate, whereby the system must be stopped and manually attended to, resulting in expensive down time. Also, even slight adherence during pick up may result in damage to the substrate, whereby the substrate must be rejected as non-usable, resulting in higher costs.
There are also several drawbacks associated with lip seals. These seals tend to slide and scuff across the substrate during compression. As a result of the sliding motion, these seals generate particulates, that result in contamination of the system. This results in rejection of substrates, as well as costly downtime from decontaminating the vacuum chambers. Moreover, the lip seals may cause the substrate to be inaccurately aligned. As discussed above, this may result in the robotic arm being unable to retrieve the substrate, or damage to the substrate, if an operator can not intervene in time.
The present invention improves on the contemporary art by providing an apparatus, typically a sealing member, for clamping an individual substrate within a plasma processing chamber via an electrostatic clamp or a mechanical clamp. The sealing member provides a seal between the substrate, for example a wafer, and the substrate support, or chuck.
The sealing member is resilient, and configured to maintain substrates with low compressive forces, so as to eliminate distortion in the substrate and the potential damage associated therewith. It is also configured to release the substrate from its clamping and sealed engagement without having the substrate stick to the surface of the clamp or the substrate support.
This sealing member clamps, seals and releases the substrate from the chuck without generating any particulates. Moreover, sealing and release of the substrate by the sealing member is such that the accuracy of the alignment of the substrate is maintained, facilitating pickup and removal by a robotic arm or other transport device, free of errors and without damaging the substrate.
The sealing member of the present invention allows sufficient, yet minimal contact area between it and the substrate, preventing leakage of the process gas in the chamber by temperature control gas supplied to the back side (underside) of the substrate, and avoids particle contamination to the upper surface of the substrate.
The sealing member has a corrugated shape, with a typically xe2x80x9cUxe2x80x9d shaped groove therein, defining this corrugated shape. This corrugated shape provides a the sealing member with spring-like behavior, to impart linear motion to substrates, facilitating removal of these substrates from the substrate support.
An embodiment disclosed herein is directed to an apparatus for sealing of a substrate on a substrate support. The apparatus has a base portion and a seal portion in communication with the base portion, and the seal portion is configured in a corrugated shape.
Another embodiment is directed to apparatus for clamping a substrate. This apparatus includes a substrate support and a clamp coupled to the substrate support, the clamp configured for moving between a first inactive position, and a second active position, where a substrate is secured to the substrate support. Also included is a corrugated shaped seal positioned around a periphery of the substrate support, the seal configured to provide a seal between the substrate support and the substrate. The clamp can be for example, a mechanical or an electrostatic clamp.
Another embodiment is directed to an apparatus for clamping a substrate within a processing chamber, for example, a plasma processing chamber. This apparatus has a clamp (for example, electrostatic or mechanical), for holding the substrate to an upper surface of a chuck, a substrate release, and a corrugated shaped seal for sealing the substrate with respect to the chuck. The seal is configured for extending around a periphery of the chuck.
Another embodiment discloses a method of sealing a substrate on a substrate support for processing. The method includes providing a corrugated shaped seal positioned around a periphery of the substrate support, the seal including a groove defining the corrugated shape, and the groove configured such that portions of said seal move between compressed and uncompressed positions. This method also includes positioning a substrate having a peripheral edge upon the seal and clamping the substrate to the substrate support, including moving the seal to a compressed position, and maintaining a sealing engagement with the substrate. Clamping can be by either mechanical or electrostatic forces.
Another embodiment is directed to a method of mechanically clamping a substrate to a substrate support. The method comprises providing a corrugated shaped seal positioned around a periphery of the substrate support, the seal including a groove defining the corrugated shape, and the groove is configured such that portions of the seal move between compressed and uncompressed positions. The method also includes positioning a substrate having a peripheral edge upon the seal, and mechanically clamping the substrate to the substrate support. This mechanical clamping including moving the seal to a compressed position, and the seal maintaining a sealing engagement with the substrate.
Another embodiment is directed to a method of electrostatically clamping a substrate to a substrate support. The method comprises providing a corrugated shaped seal positioned around a periphery of the substrate support, the seal including a groove defining the corrugated shape, and the groove is configured such that portions of the seal move between compressed and uncompressed positions. The method also includes positioning a substrate having a peripheral edge upon the seal, and electrostatically clamping the substrate to the substrate support. This electrostatic clamping including moving the seal to a compressed position, and the seal maintaining a sealing engagement with the substrate.
Throughout this document, the terms front, back, upper, lower, upward, and downward are used. These terms are indicative of typical orientations and positions for various components and structures disclosed herein, for purposes of explanation. These terms are exemplary only.